Hydrocracking can include processes which convert hydrocarbons in the presence of hydrocracking catalyst and hydrogen to more valuable products. Hydrocracking is a hydrocracking process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons. Depending on the desired output, the hydrocracking zone may contain one or more beds of the same or different catalyst. Hydrocracking is a process used to crack hydrocarbon feeds such as vacuum gas oil (VGO) to diesel including kerosene and gasoline motor fuels.
Hydrocracking can be achieved in one or two stages. In two-stage hydrocracking, hydrocracked effluent from the first stage is fractionated and unconverted oil is fed to a second stage. In single-stage hydrocracking, unconverted oil is not fed to a second stage but may be recycled to the single stage. Two-stage hydrocracking units are more expensive than one-stage units because additional equipment is required. However a two-stage unit has the advantage of providing a clean reaction environment in the second stage because the sulfur and nitrogen have been removed from the feed in the first stage and the recycle gas is typically clean, having been scrubbed before use in the second stage. More sensitive and effective hydrocracking catalysts can be used in a clean environment.
There is a need, therefore, for improved processes and apparatuses that retain the advantages of a two-stage hydrocracking reactor which minimizes equipment and operational cost.